Use new sync backup DB if settings are reset to avoid undoing reset.

chrome/browser/sync/profile_sync_service.cc

Index: chrome/browser/sync/profile_sync_service.cc
diff --git a/chrome/browser/sync/profile_sync_service.cc b/chrome/browser/sync/profile_sync_service.cc
index f4ab21aecc238e9d4cc0d9a32074e28c4ac97ded..3c387deb8a851bf65934c2262b90ad7d0babcf70 100644
--- a/chrome/browser/sync/profile_sync_service.cc
+++ b/chrome/browser/sync/profile_sync_service.cc
@@ -32,6 +32,7 @@
 #include "chrome/browser/defaults.h"
 #include "chrome/browser/invalidation/profile_invalidation_provider_factory.h"
 #include "chrome/browser/net/chrome_cookie_notification_details.h"
+#include "chrome/browser/prefs/pref_hash_filter.h"
 #include "chrome/browser/prefs/pref_service_syncable.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/services/gcm/gcm_profile_service.h"
@@ -518,14 +519,25 @@ SyncCredentials ProfileSyncService::GetCredentials() {
 }
 
 bool ProfileSyncService::ShouldDeleteSyncFolder() {
+  DVLOG(1) << "start time: " << profile_->GetStartTime().ToInternalValue()
+      << ", reset time: "
+      << PrefHashFilter::GetResetTime(profile_->GetPrefs()).ToInternalValue();

[gab, 2014/07/03 13:08:53]

Please use chrome_prefs::GetResetTime(Profile*) from
chrome_pref_service_factory.h here and below.

[haitaol1, 2014/07/07 20:43:19]

Done.

+
   if (backend_mode_ == SYNC)
     return !HasSyncSetupCompleted();
 
-  // Start fresh if it's the first time backup after user stopped syncing.
-  // This is needed because backup DB may contain items deleted by user during
-  // sync period and can cause back-from-dead issues.
-  if (backend_mode_ == BACKUP && !sync_prefs_.GetFirstSyncTime().is_null())
-    return true;
+  if (backend_mode_ == BACKUP) {
+    // Start fresh if:
+    // * It's the first time backup after user stopped syncing because backup
+    //   DB may contain items deleted by user during sync period and can cause
+    //   back-from-dead issues if user didn't choose rollback.
+    // * Settings are tampered and reset during startup to avoid undo reset.
+    if (!sync_prefs_.GetFirstSyncTime().is_null() ||
+        profile_->GetStartTime() <=
+            PrefHashFilter::GetResetTime(profile_->GetPrefs())) {
+      return true;
+    }
+  }
 
   return false;
 }